Effect of heat treatment on bentonites for utilization as a supplementary cementitious material

This study evaluated the potential of thermally activated bentonite to reduce clinker usage and CO2 emissions in cement production. Three bentonites of different geological origins (from U.S.A. Korea, and India) were heat-treated at 700°C to destabilize their layered structures and induce partial amorphization. The structural transformations were characterized using XRD and FTIR, and pozzolanic activity was assessed through thermogravimetric analysis and compressive strength. The results revealed that Gampo (Korea) bentonite exhibited clear pozzolanic activity, enabling 20–30% replacement of cement with comparable or improved compressive strength. In contrast, Californian bentonite remained largely inert under identical treatment. Thermodynamic modeling validated experimental findings by predicting the formation of substantial C–A–S–H and hydrotalcite phases for the reactive sources. This study showed that regionally available bentonite can be used as a supplementary cementitious material after optimal heat treatment, aligning with global strategies to reduce CO2 footprint of construction materials.